Drilling a well (e.g., oil, gas) is a complex, time-consuming, and expensive endeavor. Often, experts such as geologists manually collect the results of seismic studies, data from other wells drilled near the target location, and other information. From such data, the geologist generates a geological model of the various formations below the surface of the drilling rig. The geological model also includes depths to the various “tops” that define the formations. The term “top” generally refers to the top of a horizon, a fault, stratigraphic or biostratigraphic boundaries of significance pore pressure transition zones, etc. A typical geological model includes multiple tops defining the presence and geometry of such subsurface features, as well as the composition of such subsurface features.
A “well plan” is developed based, at least in part, on the geological model. The well plan specifies a number of parameters for drilling the target well such as the mud weight, drill bit rotational speed, and weight-on-bit (WOB). The workers on the drilling rig control the operation of the drill bit commensurate with the well plan. For example, the rig workers may want to reduce the rate of penetration (ROP) in a harder rock formation to prevent damage to the cutters on the drill bit. Thus, the rig workers typically rely on the well plan to anticipate tops and drilling uncertainties, and adjust drilling parameters accordingly; without the well plan, the rig workers would not know the location of the various tops and associated drilling uncertainties.
Oftentimes, the initial geological model is not completely accurate. For example, the actual distance from the surface to a particular top might be different than the estimated distance in the initial well plan by a number of feet. Most geological models recite distances from the surface down to a particular top, the distance between two subsurface tops, or combinations thereof. Thus, if the location of a particular top in the well plan turns out to be inaccurate, that error may have an effect for all other tops whose locations are specified relative to the former top. Such inaccuracies in the geological model impact the well plan and inhibit the ability of the rig workers to anticipate tops and drilling uncertainties.
Drill strings and surface equipment include numerous sensors and devices that monitor a wide variety of parameters such as hole depth, bit depth, mud weight, choke pressure, etc. Such information can be used to determine the accuracy of the initial well geological model. However, the data generated in real-time during drilling operations is voluminous, and in many cases, personnel on the drilling rig are not equipped and/or may not have the time to review and interpret the vast quantity of collected data at the well site. Instead, some of the monitored data can be transmitted back to the geologist at a remote site for further analysis and interpretation. Because the rig can be in a remote location (e.g., off shore) the communication link for such transmissions usually involves satellite communications which may not have sufficient bandwidth to transmit the vast quantity of information being acquired at the well site. Due, at least in part, to the bandwidth limitations, some, but not all, of the acquired sensor data is transmitted back to the geologist at the remote location. For example, a particular sensor may take a sample reading every one-half second but only every fifth of those readings (representing one reading every 2.5 seconds) is actually transmitted back to the geologist. As a result, the geologist may miss crucial information because he/she is provided less than all of the data. Further, even if all sensor data from the well site could be transmitted back to the geologist, it may take a significant amount of time for the geologist to interpret the information, update the geological model and well plan and transmit the updated plan back to the well site. However, due to the cost and time sensitive nature of drilling, drilling operations continue while the rig workers await the updated well plan from the geologist. Drilling continues in the face of potentially inaccurate information due to the lengthy time lag as the well plan is updated and communicated back the rig.